Dynamics in Year-Class Strength, Growth, and Calcified-Structure Size of Native Lake Trout (Salvelinus namaycush) Exposed to Moderate Acidification and Whole-Lake Neutralization

1992 ◽  
Vol 49 (S1) ◽  
pp. 102-113 ◽  
Author(s):  
John M. Casselman ◽  
John M. Gunn
Keyword(s):  
Water Quality ◽  
Direct Effect ◽  
Lake Trout ◽  
Calcium Content ◽  
Salvelinus Namaycush ◽  
Ambient Water ◽  
Intraspecific Interaction ◽  
Relative Growth ◽  
Class Strength

Accurate age-interpretation techniques were developed, using scales and otoliths, to examine the role of whole-lake neutralization in the resurgence of a lake trout (Salvelinus namaycush) fishery in Nelson Lake (pH 5.7) near Sudbury, Ontario. Calcified structures and data from 860 lake trout were collected from 1972 to 1987. The population was characterized by the regular cyclic occurrence of strong year classes, which were probably an effect of pulse angling, cyclic food abundance, and possibly intraspecific interaction. The majority (65.8%) of the lake trout caught in the exceptional winter fishery of 1980 (3.3 kg∙ha−1) were in the lake prior to liming in 1975–76. Young lake trout (up to age 4) of the 1975 and 1976 year classes grew bigger and had larger scales than other year classes from 1973 to 1977, coinciding with an increase in hypolimnetic zooplankton, probably related to improved water quality. Otoliths grew significantly larger and more translucent and exceeded relative growth of scales and body for all ages in 1976 (18% greater) and for the 1976 year class, confirming that otolith accretion can come from the ambient water because liming increased the calcium content by 33% that year, the only observed direct effect of the treatment.

Changes in the Zoobenthos Community of Acidified Bowland Lake after Whole-Lake Neutralization and Lake Trout (Salvelinus namaycush) Reintroduction

1990 ◽  
Vol 47 (2) ◽  
pp. 440-445 ◽  
Author(s):  
W. Keller ◽  
Lewis A. Molot ◽  
Ronald W. Griffiths ◽  
N. D. Yan
Keyword(s):  
Water Quality ◽  
Fish Community ◽  
Lake Trout ◽  
Size Structure ◽  
Salvelinus Namaycush ◽  
Total Abundance ◽  
Insufficient Time

The zoobenthos of Bowland Lake is described prior to, and for 2 yr after, neutralization of the lake from pH 4.9 to > 6.0 and reintroduction of lake trout (Salvelinus namaycush). Observed changes in the total abundance, biomass, and size structure of shallow and profundal zoobenthos assemblages were attributable to changes in the fish community, not to improvements in water quality. A shift toward increased importance of oligochaetes, more representative of nonacidic conditions, occurred. However, many common, acid-sensitive taxa of zoobenthos which were absent prior to neutralization had not appeared within 2 yr after treatment, indicating insufficient time for recolonization.

Effects of experimental clearcut logging on water quality in three small boreal forest lake trout (Salvelinus namaycush) lakes

2000 ◽  
Vol 57 (S2) ◽  
pp. 92-96 ◽  
Author(s):  
Robert J Steedman
Keyword(s):  
Water Quality ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Lake Trout ◽  
Salvelinus Namaycush ◽  
First Year ◽  
Forest Lake ◽  
Clearcut Logging ◽  
Quality Response ◽  
Shield Lakes

Water quality was monitored in three 30-ha stratified headwater Precambrian Shield lakes for 5 years before and 3 years after moderate to extensive catchment deforestation. These lakes, which had water renewal times of about a decade, showed only minor changes in water quality by the third year after logging. Water quality response in a lake with moderate deforestation and intact shoreline forest was similar to that in two lakes with extensive upland and shoreline deforestation. By the second and third years after logging, May-September average volume-weighted concentrations of dissolved organic carbon, chlorophyll, total nitrogen, K+, Cl-, and Si had all increased, generally by about 10-40% over predisturbance levels, while Ca2+ and Mg2+ had declined by 10-25%. Dry weather the first year after logging was associated with temporary declines of 10-20% in dissolved organic carbon and chlorophyll.

Decline and Recovery of the Lake Superior Gull Island Reef Lake Trout (Salvelinus namaycush) Population and the Role of Sea Lamprey (Petromyzon marinus) Predation

1980 ◽  
Vol 37 (11) ◽  
pp. 2074-2080 ◽  
Author(s):  
Bruce L. Swanson ◽  
Donald V. Swedberg
Keyword(s):  
Lake Trout ◽  
Lake Superior ◽  
Petromyzon Marinus ◽  
Total Mortality ◽  
Mortality Rates ◽  
Sea Lamprey ◽  
Salvelinus Namaycush ◽  
Steady Increase ◽  
Egg Deposition

The Gull Island Reef lake trout (Salvelinus namaycush) population was one of the few in Lake Superior that was not annihilated by the combined effects of excessive fishing and sea lamprey (Petromyzon marinus) predation. Following control of the lamprey in the early 1960s, this population of lake trout began a slow but steady increase in the average age and numbers of lake trout. Total annual mortality rates for spawning lake trout were 32% for age VI fish, 48% for ages VII–VIII, and 75% for ages IX and older. These total mortality rates included a 7.3% exploitation rate u, a 20% natural mortality n, and annual lamprey-induced mortalities of 6% for ages V–VI, 24%, for ages VII–VIII, and 56% for ages IX and older fish. The estimated number of lake trout eggs deposited annually on Gull Island Reef from 1964 to 1979 ranged from 3.3 million eggs in 1965 to 28 million eggs in 1979, with a mean of 9 million eggs per year. At present levels of lamprey predation, the estimated egg to spawning fish return rate on Gull Island Reef is 0.18%.Key words: lake trout, sea lamprey, survival, population structure, egg deposition

Prediction of Lake Trout (Salvelinus namaycush) Presence in Low-Alkalinity Lakes near Sudbury, Ontario

1992 ◽  
Vol 49 (S1) ◽  
pp. 95-101 ◽  
Author(s):  
Michael Conlon ◽  
John M. Gunn ◽  
J. Robert Morris
Keyword(s):  
Water Quality ◽  
Fish Community ◽  
Acidic Deposition ◽  
Lake Trout ◽  
Salvelinus Namaycush ◽  
Species Assemblages ◽  
Fish Community Structure ◽  
The Status ◽  
Measured Water ◽  
Correct Discrimination

Surveys of 30 low-alkalinity lake trout (Salvelinus namaycush) lakes near Sudbury, Ontario, were conducted to assess factors that affect lake trout presence under acidification stress. At the time of the surveys the lakes varied widely in pH (4.5–6.9), concentrations of toxic metals (Al 12–300 μg∙L−1), and the status of lake trout populations (extinct–abundant). Fish community structure (species richness, species assemblages) reflected and was readily predicted from measured water quality variables. A PCA factor composed of pH, alkalinity, and conductivity was the variable that best predicted lake trout presence (correct discrimination (> 92%). The results of this study provide managers with easily obtainable predictors for monitoring lake trout status under changing levels of acidic deposition.

Estimated Impacts of SO2 Emissions from Sudbury Smelters on Ontario's Sportfish Populations

1992 ◽  
Vol 49 (S1) ◽  
pp. 87-94 ◽  
Author(s):  
John E. Matuszek ◽  
Donna L. Wales ◽  
John M. Gunn
Keyword(s):  
Water Quality ◽  
Brook Trout ◽  
Lake Trout ◽  
Salvelinus Namaycush ◽  
Smallmouth Bass ◽  
Micropterus Dolomieu ◽  
Quality Improvements ◽  
So2 Emissions ◽  
Acidic Lakes ◽  
Local Impacts

Impacts of acidification on the major sportfish species in Ontario (lake trout (Salvelinus namaycush), brook trout (S. fontinalis), smallmouth bass (Micropterus dolomieu), and walleye (Stizostedion vitreum)) were estimated from the results of extensive water quality surveys conducted during the period 1978–85. Local impacts, within the 17 000 km2 area most affected by emissions from Sudbury smelters, were also estimated and compared with the provincial values. The estimated numbers of acidic lakes in Ontario in which viable sportfish populations have disappeared were 119 lake trout lakes (5.1% of known lake trout lakes), 34 brook trout lakes (1.6%), 52 smallmouth bass lakes (2.2%), and 14 walleye lakes (0.3%). Most of these affected lakes were in the Sudbury zone, where fish populations, particularly those of lake trout, began declining more than 30 yr ago. The estimated numbers of critically acidic lakes in the Sudbury zone were 94 lake trout lakes, 14 brook trout lakes, 18 smallmouth bass lakes, and 7 walleye lakes. More recent sampling of a subset of Sudbury lakes indicated that substantial water quality improvements have occurred as a result of emission reductions from Sudbury smelters.

Improved interpretation of labelled fish otoliths: a cost-effective tool in sustainable fisheries management

2005 ◽  
Vol 56 (5) ◽  
pp. 705 ◽  
Author(s):  
T. Niva ◽  
P. Keränen ◽  
J. Raitaniemi ◽  
H. M. Berger
Keyword(s):  
Salmo Trutta ◽  
Lake Trout ◽  
Salvelinus Alpinus ◽  
Arctic Charr ◽  
Cost Effective ◽  
Salvelinus Namaycush ◽  
Sander Lucioperca ◽  
Alizarin Red ◽  
Brown Trout Salmo Trutta

A total of 222 pairs of alizarin red S (ARS)-labelled and 75 pairs of unlabelled sagittal otoliths from six hatchery-reared species, including Arctic charr (Salvelinus alpinus (L.)), lake trout (Salvelinus namaycush (Walbaum)), salmon (Salmo salar L.), brown trout (Salmo trutta L.), whitefish (Coregonus sp.) and pikeperch (Sander lucioperca (L.)), were used in blind tests to determine whether sawing a 0.4-mm thick slice from the otolith would improve the interpretation of labelled otoliths. The fish were labelled in 1995–2002. Fish age at labelling varied from two weeks to three months, immersion time from three to six hours and concentration of ARS 50–100 ppm. Blind tests were arranged so that sawed slices were contrasted with entire otoliths using stereomicroscope under UV epi-illumination. According to blind tests, the accuracy of interpretation of ARS-labelled otoliths was 97.0% from the slices and 92.3% from entire otoliths. The role of different filters in detecting false marks owing to autofluorescence is discussed. Cost-benefits of the method are discussed briefly.

The Influence of Competency of Preschool Teachers in Fujian Province on Subjective Well-Being: The Mediating Role of Psychological Capital

2019 ◽  
Author(s):  
Xuguang Sun ◽  
Ailing Huang
Keyword(s):  
Direct Effect ◽  
Psychological Capital ◽  
Preschool Teachers ◽  
Well Being ◽  
Mediating Effect ◽  
Subjective Well Being ◽  
Positive Psychological Capital ◽  
Mediating Role ◽  
Mediator Variable

The intermediary effect interval of the preschool teachers' competence characteristics → positive psychological capital → the subjective well-being of the preschool teachers is (0.23—0.55), does not contain 0, and the effect amount is 0.35. The competency characteristics of preschool teachers → The direct effect interval of subjective well-being of preschool teachers is (0.05—0.36), excluding 0, and the effect quantity is 0.20, indicating that positive psychological capital as a mediator variable has the characteristics of preschool teachers and the subjective well-being of preschool teachers. Partial mediating effect, the ratio of mediating effect to total effect is 64.01%.

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